P0136 Code

2004 Tundra 4.7L with 209K miles. Runs like new except.....

The Bank 1 Sensor 2 (B1S2) is showing a pending P0136. I expect that once I drive the Tundra some more, it will throw the code and my check engine light will come on. The B1S1 and B1S2 O2 sensors were just replaced yesterday with Denso brand sensors to address a P0420 code. That P0420 code hasn't reappeared thus far and all was OK until I got about 15 miles with the new sensors and which time the pending P0136 started to appear.
I hooked up an Actron OBII reader and it is showing a fairly steady .015 reading for B1S2.
B1S1 voltage is oscillating as I believe it should between .05v to .9v approximately.

In comparison, B2S1 is also oscillating within a similar range as does B2S1 and B2S2 is oscillating but at a much lower voltage range. From the bit that I read this broad voltage oscillation range at B2S1 and lower and narrower voltage range oscillation at B2S2 is what it should be.
The B2 side hasn't throwing any codes thus far so I am using it as a guide to compare with the problem Bank 1 side.

A bit more info....the exhaust pipe where B1S2 mounts was too corroded so the shop that installed the sensors fabricated a new section of pipe that includes a new O2 mounting plate section. I haven't looked at it so it's possible there is a leak possibly where the flange joins with the cat. If that is loose and pulling air I believe the voltage will be constantly showing a too lean condition, which is what it's doing.

So besides taking a closer look at this possibility, what might be other causes for the P0136?
Thanks!

 

Man. Looks like you covered all the bases with one of the most thorough analysis I’ve seen on this subject. Not sure what to add, but sounds like you will track it down.

 

Bottom line... the Bank 1 Sensor 2 appears to show .015mv reading almost constantly. Moves up to .035 when accelerating.